The present invention relates to a laser device for emitting a plurality of laser beams, which are coaxially superimposed on each other.
A medical treatment system using a laser beam is now widely known. By irradiating laser beams, the system is used for performing photocoagulation, resection, incision, etc. of an affected site of a patient on non-contact basis. Color of each of the laser beams, i.e. a wavelength of the laser beam used in the device differs according to the type of medical treatment. For a laser device for emitting a laser beam to be used in a medical treatment system, it is desirable that laser beams with a plurality of wavelengths can be sent to the medical treatment system.
As a laser device for emitting laser beams with a plurality of wavelengths, a device shown in FIG. 5 has been known in the past. A medical treatment system (a slit lamp) 19 using the laser device is shown in FIG. 6.
FIG. 5 represents general concept of a laser device. In the figure, reference numeral 1 denotes a laser device, and 2 denotes an optical fiber for propagation to guide the laser beams from the laser device 1 toward the medical treatment system 19. An output unit of the laser device 1 is connected with the optical fiber 2 for propagation via an optical connector 3 so that it can be attached to or removed from the optical fiber.
As laser beam emitting sources, a laser beam light source unit 10 comprises a first laser oscillator 4 for emitting a laser beam 7 with a wavelength of λ1, a second laser oscillator 5 for emitting a laser beam 8 with a wavelength of λ2, and a third laser oscillator 6 for emitting a laser beam 9 with a wavelength of λ3. The laser beams 7, 8 and 9 emitted respectively from the first laser oscillator 4, the second laser oscillator 5, and the third laser oscillator 6 are superimposed on each other on a same axis via a beam multiplexer 11.
The beam multiplexer 11 comprises a first multiplexer 12 and a second multiplexer 13 arranged on an optical axis of the laser beam 7. It has a deflection mirror 14 on an optical axis of the laser beam 8 and has a deflection mirror 15 on an optical axis of the laser beam 9. The first multiplexer 12 allows the laser beam 7 with the wavelength of λ1 to pass, while the first multiplexer 12 reflects the laser beam 8 with the wavelength of λ2. The second multiplexer 13 allows the laser beams 7 and 8 to pass, while the second multiplexer 13 reflects the laser beam 9 with the wavelength of λ3.
The laser beam 7 emitted from the first laser oscillator 4 passes through the first multiplexer 12 and the second multiplexer 13 and enters a condenser lens 17. The laser beam 8 is reflected by the deflection mirror 14 and the first multiplexer 12. After being superimposed on the same optical axis as the laser beam 7, the laser beam 8 passes through the second multiplexer 13 and enters the condenser lens 17. The laser beam 9 is reflected by the deflection mirror 15 and the second multiplexer 13. The laser beam 9 is then superimposed on the same optical axis as the laser beams 7 and 8 and enters the condenser lens 17 as a coaxial multi-laser beam 16. The condenser lens 17 converges the coaxial multi-laser beam 16 and allows the laser beam to enter the optical fiber 2 for propagation via the optical connector 3. The optical fiber 2 for propagation guides the coaxial multi-laser beams 16 toward a medical treatment system such as a photocoagulator, a slit lamp, etc.
In the conventional type laser device as described above, it is difficult that optical axes of the laser beams 7, 8 and 9 perfectly concur with each other. Further, the laser beams 7, 8 and 9 do not necessarily have the same numerical aperture (NA). When the laser beams 7, 8 and 9 converged by the condenser 17 have different numerical apertures, it is difficult that all of the laser beams 7, 8 and 9 enter the optical fiber 2 for propagation without optical loss when the laser device 1 and the optical fiber 2 are connected via the optical connector 3. It is also difficult that these laser beams enter the optical fiber 2 for propagation under the completely same condition without causing the deviation of the optical axis.
For this reason, when the laser beams are projected to the site to be treated of a patient, troubles often occur such as the development of speckles in light intensity distribution at an irradiating point.